1<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" 2 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" 3 [<!ENTITY mdash "—">]> 4<!-- 5 - Copyright (C) 2004, 2005, 2007-2009, 2014 Internet Systems Consortium, Inc. ("ISC") 6 - Copyright (C) 2000-2002 Internet Software Consortium. 7 - 8 - Permission to use, copy, modify, and/or distribute this software for any 9 - purpose with or without fee is hereby granted, provided that the above 10 - copyright notice and this permission notice appear in all copies. 11 - 12 - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 13 - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 14 - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 15 - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 16 - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 17 - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 18 - PERFORMANCE OF THIS SOFTWARE. 19--> 20 21<refentry id="man.host"> 22 23 <refentryinfo> 24 <date>January 20, 2009</date> 25 </refentryinfo> 26 27 <refmeta> 28 <refentrytitle>host</refentrytitle> 29 <manvolnum>1</manvolnum> 30 <refmiscinfo>BIND9</refmiscinfo> 31 </refmeta> 32 33 <refnamediv> 34 <refname>host</refname> 35 <refpurpose>DNS lookup utility</refpurpose> 36 </refnamediv> 37 38 <docinfo> 39 <copyright> 40 <year>2004</year> 41 <year>2005</year> 42 <year>2007</year> 43 <year>2008</year> 44 <year>2009</year> 45 <year>2014</year> 46 <holder>Internet Systems Consortium, Inc. ("ISC")</holder> 47 </copyright> 48 <copyright> 49 <year>2000</year> 50 <year>2001</year> 51 <year>2002</year> 52 <holder>Internet Software Consortium.</holder> 53 </copyright> 54 </docinfo> 55 56 <refsynopsisdiv> 57 <cmdsynopsis> 58 <command>host</command> 59 <arg><option>-aCdlnrsTwv</option></arg> 60 <arg><option>-c <replaceable class="parameter">class</replaceable></option></arg> 61 <arg><option>-N <replaceable class="parameter">ndots</replaceable></option></arg> 62 <arg><option>-R <replaceable class="parameter">number</replaceable></option></arg> 63 <arg><option>-t <replaceable class="parameter">type</replaceable></option></arg> 64 <arg><option>-W <replaceable class="parameter">wait</replaceable></option></arg> 65 <arg><option>-m <replaceable class="parameter">flag</replaceable></option></arg> 66 <arg><option>-4</option></arg> 67 <arg><option>-6</option></arg> 68 <arg><option>-v</option></arg> 69 <arg><option>-V</option></arg> 70 <arg choice="req">name</arg> 71 <arg choice="opt">server</arg> 72 </cmdsynopsis> 73 </refsynopsisdiv> 74 75 <refsect1> 76 <title>DESCRIPTION</title> 77 78 <para><command>host</command> 79 is a simple utility for performing DNS lookups. 80 It is normally used to convert names to IP addresses and vice versa. 81 When no arguments or options are given, 82 <command>host</command> 83 prints a short summary of its command line arguments and options. 84 </para> 85 86 <para><parameter>name</parameter> is the domain name that is to be 87 looked 88 up. It can also be a dotted-decimal IPv4 address or a colon-delimited 89 IPv6 address, in which case <command>host</command> will by 90 default 91 perform a reverse lookup for that address. 92 <parameter>server</parameter> is an optional argument which 93 is either 94 the name or IP address of the name server that <command>host</command> 95 should query instead of the server or servers listed in 96 <filename>/etc/resolv.conf</filename>. 97 </para> 98 99 <para> 100 The <option>-a</option> (all) option is equivalent to setting the 101 <option>-v</option> option and asking <command>host</command> to make 102 a query of type ANY. 103 </para> 104 105 <para> 106 When the <option>-C</option> option is used, <command>host</command> 107 will attempt to display the SOA records for zone 108 <parameter>name</parameter> from all the listed 109 authoritative name 110 servers for that zone. The list of name servers is defined by the NS 111 records that are found for the zone. 112 </para> 113 114 <para> 115 The <option>-c</option> option instructs to make a DNS query of class 116 <parameter>class</parameter>. This can be used to lookup 117 Hesiod or 118 Chaosnet class resource records. The default class is IN (Internet). 119 </para> 120 121 <para> 122 Verbose output is generated by <command>host</command> when 123 the 124 <option>-d</option> or <option>-v</option> option is used. The two 125 options are equivalent. They have been provided for backwards 126 compatibility. In previous versions, the <option>-d</option> option 127 switched on debugging traces and <option>-v</option> enabled verbose 128 output. 129 </para> 130 131 <para> 132 List mode is selected by the <option>-l</option> option. This makes 133 <command>host</command> perform a zone transfer for zone 134 <parameter>name</parameter>. Transfer the zone printing out 135 the NS, PTR 136 and address records (A/AAAA). If combined with <option>-a</option> 137 all records will be printed. 138 </para> 139 140 <para> 141 The <option>-i</option> 142 option specifies that reverse lookups of IPv6 addresses should 143 use the IP6.INT domain as defined in RFC1886. 144 The default is to use IP6.ARPA. 145 </para> 146 147 <para> 148 The <option>-N</option> option sets the number of dots that have to be 149 in <parameter>name</parameter> for it to be considered 150 absolute. The 151 default value is that defined using the ndots statement in 152 <filename>/etc/resolv.conf</filename>, or 1 if no ndots 153 statement is 154 present. Names with fewer dots are interpreted as relative names and 155 will be searched for in the domains listed in the <type>search</type> 156 or <type>domain</type> directive in 157 <filename>/etc/resolv.conf</filename>. 158 </para> 159 160 <para> 161 The number of UDP retries for a lookup can be changed with the 162 <option>-R</option> option. <parameter>number</parameter> 163 indicates 164 how many times <command>host</command> will repeat a query 165 that does 166 not get answered. The default number of retries is 1. If 167 <parameter>number</parameter> is negative or zero, the 168 number of 169 retries will default to 1. 170 </para> 171 172 <para> 173 Non-recursive queries can be made via the <option>-r</option> option. 174 Setting this option clears the <type>RD</type> — recursion 175 desired — bit in the query which <command>host</command> makes. 176 This should mean that the name server receiving the query will not 177 attempt to resolve <parameter>name</parameter>. The 178 <option>-r</option> option enables <command>host</command> 179 to mimic 180 the behavior of a name server by making non-recursive queries and 181 expecting to receive answers to those queries that are usually 182 referrals to other name servers. 183 </para> 184 185 <para> 186 By default, <command>host</command> uses UDP when making 187 queries. The 188 <option>-T</option> option makes it use a TCP connection when querying 189 the name server. TCP will be automatically selected for queries that 190 require it, such as zone transfer (AXFR) requests. 191 </para> 192 193 <para> 194 The <option>-4</option> option forces <command>host</command> to only 195 use IPv4 query transport. The <option>-6</option> option forces 196 <command>host</command> to only use IPv6 query transport. 197 </para> 198 199 <para> 200 The <option>-t</option> option is used to select the query type. 201 <parameter>type</parameter> can be any recognized query 202 type: CNAME, 203 NS, SOA, SIG, KEY, AXFR, etc. When no query type is specified, 204 <command>host</command> automatically selects an appropriate 205 query 206 type. By default, it looks for A, AAAA, and MX records, but if the 207 <option>-C</option> option was given, queries will be made for SOA 208 records, and if <parameter>name</parameter> is a 209 dotted-decimal IPv4 210 address or colon-delimited IPv6 address, <command>host</command> will 211 query for PTR records. If a query type of IXFR is chosen the starting 212 serial number can be specified by appending an equal followed by the 213 starting serial number (e.g. -t IXFR=12345678). 214 </para> 215 216 <para> 217 The time to wait for a reply can be controlled through the 218 <option>-W</option> and <option>-w</option> options. The 219 <option>-W</option> option makes <command>host</command> 220 wait for 221 <parameter>wait</parameter> seconds. If <parameter>wait</parameter> 222 is less than one, the wait interval is set to one second. When the 223 <option>-w</option> option is used, <command>host</command> 224 will 225 effectively wait forever for a reply. The time to wait for a response 226 will be set to the number of seconds given by the hardware's maximum 227 value for an integer quantity. 228 </para> 229 230 <para> 231 The <option>-s</option> option tells <command>host</command> 232 <emphasis>not</emphasis> to send the query to the next nameserver 233 if any server responds with a SERVFAIL response, which is the 234 reverse of normal stub resolver behavior. 235 </para> 236 237 <para> 238 The <option>-m</option> can be used to set the memory usage debugging 239 flags 240 <parameter>record</parameter>, <parameter>usage</parameter> and 241 <parameter>trace</parameter>. 242 </para> 243 244 <para> 245 The <option>-V</option> option causes <command>host</command> 246 to print the version number and exit. 247 </para> 248 </refsect1> 249 250 <refsect1> 251 <title>IDN SUPPORT</title> 252 <para> 253 If <command>host</command> has been built with IDN (internationalized 254 domain name) support, it can accept and display non-ASCII domain names. 255 <command>host</command> appropriately converts character encoding of 256 domain name before sending a request to DNS server or displaying a 257 reply from the server. 258 If you'd like to turn off the IDN support for some reason, defines 259 the <envar>IDN_DISABLE</envar> environment variable. 260 The IDN support is disabled if the variable is set when 261 <command>host</command> runs. 262 </para> 263 </refsect1> 264 265 <refsect1> 266 <title>FILES</title> 267 <para><filename>/etc/resolv.conf</filename> 268 </para> 269 </refsect1> 270 271 <refsect1> 272 <title>SEE ALSO</title> 273 <para><citerefentry> 274 <refentrytitle>dig</refentrytitle><manvolnum>1</manvolnum> 275 </citerefentry>, 276 <citerefentry> 277 <refentrytitle>named</refentrytitle><manvolnum>8</manvolnum> 278 </citerefentry>. 279 </para> 280 281 </refsect1> 282</refentry><!-- 283 - Local variables: 284 - mode: sgml 285 - End: 286--> 287